1. Field of the Invention
The present invention relates to a technique of setting an encryption key, which is used to encrypt radio communication data transmitted between an access point as a relay station for a wireless LAN and a terminal equipped with a device for connecting with the wireless LAN prior to the transmission, in the terminal and in the access point.
2. Description of the Related Art
Access points as radio relay stations for a wireless LAN are used as the device of connecting multiple computers at separate locations to the Internet not only in the places where specific people continuously act; such as homes and offices (hereafter referred to as private spaces), but in the places where general public temporarily act, such as hotels, airports, shopping malls, parks, and stations (hereafter referred to as public spaces) One proposed technique connects an access point located in a public space with a broadband line, which ensures high-speed Internet access service, such as an xDSL line or a CATV line, and gives a space for Internet access (hereafter referred to as a free spot) to the general public in the coverage of radio wave transmitted from the access point (radio communication area). The administrator of the public space is authorized to use a certain broadband line. The broadband line is open to terminals possessed by the respective users of the public space via the access point for the wireless LAN. This enhances the convenience of the user's Internet access and increases the utilization rate of the public space.
The free space may give only limited people (for example, clients) the authorization for access to the Internet via the wireless LAN in the radio communication area. In such cases, it is required to prevent illegal access of any unauthorized person to the network. A number of people use the same free spot, and the radio waves for wireless communication are frequently transmitted between terminals possessed by the respective people and the access point. For sufficient protection of privacy of each person, it is essential to effectively prevent the contents of communication from being leaked to any third person by interception of the radio waves in the radio communication area.
Diverse security techniques for preventing illegal access to the network and leakage of communication to any third person have been proposed with regard to the wireless LAN. One proposed technique utilizes a MAC (Media Access Control) address, which is an intrinsic identification number allocated to a device for connecting the wireless LAN (for example, a wireless LAN adapter) attached to the terminal, and registers the allocated MAC address in the access point. The access point authenticates the MAC address in response to an access from the terminal, and rejects the request of access to the network from the terminal when the input MAC address is not identical with the registered MAC address. This technique is referred to as the MAC address restriction technique (for example, see Japanese Patent Laid-Open Gazette No. 2001-320373). Another proposed technique sets a WEP (Wired Equivalent Privacy) key as a common encryption key in both the terminal and the access point and encrypts the details of the data, which are transmitted between the terminal and the access point, with the WEP key. Even in the case of accidental leakage of data, the encryption makes it difficult to analyze and grasp the data. This technique is referred to as the WEP encryption technique (for example, see Japanese Patent Laid-Open Gazette No. 2001-345819).
In order to ensure the high security level of the free spot, each user who wants to utilize the free spot is required to register the MAC address and set the WEP key with regard to the terminal of the user, prior to use of the free spot.
The prior art security technique, however, requires manual registration of the MAC address in the access point and manual setting of the WEP key in the terminal, and is rather troublesome and inconvenient in the case of new enrollment of a terminal for the wireless LAN. Especially in the case of a free spot installed in a public space, there are a large number of users who want to utilize the free spot, and the number is increasing. It is extremely inconvenient and unpractical to ask each of the many users who possess own terminals to operate the terminal for registration of the MAC address and setting of the WEP key as the conditions of utilizing the free spot.
The WEP key of an arbitrary letter string set in the terminal should also be set in the access point. It is preferable to utilize the wireless LAN for the setting. The WEP key data carried on the radio wave is transmitted from the terminal to the access point by wireless. The access point receives the transmitted WEP key and sets the WEP key mapped to the terminal. The user of the terminal is then allowed to enjoy various services (for example, Internet access service) via the wireless LAN immediately after transmission of the WEP key. In the case of wireless transmission of the WEP key, however, there is a possibility of leakage of the WEP key to a third person through interception of the radio wave transmitted between the terminal and the access point. The third person who illegally obtains the leaked WEP key can analyze and grasp all the data transmitted between the access point and the terminal with the WEP key. This disables the security system based on encryption. Especially in the access point of the free spot, the WEP key is set in the terminals of many users who want to utilize the free spot. It is thus highly demanded to effectively prevent leakage of the WEP key and ensure sufficient secrecy of communication for a large number of users.